Archive · 13 Aug 2026
Heatwave expected to cut 15% of France's nuclear capacity Friday
France gets about 70% of its electricity from nuclear power plants, which need cool river water to run safely.
The law says plants cannot make river water too hot, to protect the environment.
When the weather gets very hot, rivers warm up, so nuclear plants have to make less electricity.
Europe has already faced five heatwaves this summer, and the newest one is bringing very hot weather again.
On Friday, six French reactors will be fully stopped, cutting nuclear power by about 15%.
Because there is less power, electricity prices go up.
France also sends less electricity to its neighbours, so countries like Britain and Germany will burn more coal and gas.
There is even some trouble from jellyfish, which blocked the water intake at one nuclear plant, keeping two reactors offline.
Experts say it is the lowest amount of French nuclear power available since August 2023.
Europe's fifth heatwave this summer is expected to cut French nuclear output by about 15% of fleet capacity on Friday, with six reactors fully offline.
Around 27.7 GW of nuclear power is expected to be offline on Friday due to heat, maintenance, technical issues and fuel saving, the lowest availability since August 2023.
French day-ahead power prices for Friday rose 4.4% to €154.50 per megawatt hour, the highest since June 23.
Reduced French nuclear exports are forcing countries such as Britain and Germany to turn on coal and gas plants.
Two jellyfish-affected reactors at France's Gravelines plant are expected to remain offline for several more days.
- Who
- France's nuclear operator EDF and the French nuclear fleet; affected neighbours include Britain and Germany.
- What
- A heatwave is expected to cut French nuclear power production by about 15% of fleet capacity on Friday, with six reactors fully offline, raising power prices.
- When
- On Friday, during Europe's fifth heatwave this summer; the article is dated Aug 13, with Thursday expected as the heatwave's peak.
- Where
- France, with knock-on effects on electricity supply across Europe, including Britain and Germany.
- Why
- Environmental rules limit how much heat nuclear plants can discharge into rivers, forcing output cuts as water temperatures rise during the heatwave.
- Nuclear capacity cut
- About 15% of French nuclear fleet capacity on Friday
- Reactors fully offline
- 6
- Total nuclear offline on Friday
- ~27.7 GW — lowest since August 2023
- Day-ahead power price for Friday
- €154.50/MWh, up 4.4% (highest since June 23)
- Nuclear share of French electricity
- About 70% of annual production
- Heatwave peak temperatures
- 35–40°C in most regions on Thursday
- Countries turning to coal and gas
- Britain and Germany
- Gravelines jellyfish-hit reactors
- Two expected offline for several more days